We plan to continue in the analysis of resistance plasmids from a variety of gram negative and gram positive organisms, the goals are to: a) determine mechanisms of resistance, b) establish relationships between similar mechanisms of resistance in unrelated organisms, c) carry out structural studies on resistance plasmids with particular 0eference to transposable elements and the mechanism of transposition. In addition, this project will analyze the mechanisms by which aminoglycoside antibiotics are taken up by cells; we will analyze the transport mechanisms in detail by use of mutants and membrane characterization.